While not as famous as some of their other collaborations (such as THE BLACK CAT and THE BODY SNATCHER), this is a dandy little horror film even though the casting decisions were a bit odd. Boris Karloff plays Dr. Janos Rukh, a weird scientist who lives in the Carpathian mountains--near where the Dracula character's home town. Bela Lugosi plays Dr. Benet--whose nationality was never discussed though the name certainly sounds French. I really think it would have made sense to have the two switch roles, as the Carpathian role seems tailor made for Lugosi--especially with his accent. However, despite this unusual twist, the two still did excellent jobs. Karloff's was definitely the lead role, but Lugosi acquitted himself well as a relatively normal person--something he didn't play very often in films!! It seems that Dr. Rukh is a bit of a pariah, as other scientists (especially Benet) think his theories are bizarre and nonsensical. However, over the course of the film, Rukh turns out to be right and Benet is especially generous in his new praise for Rukh. But, unfortunately, the wonderful new element that Rukh discovered has the nasty side effect of turning him into a crazy killing machine (don't you hate it when that happens?). While this could have just been a simple nice scientist turned mad story, the plot was well constructed, the characters nicely developed and the mad Rukh was NOT a one-dimensional killer, but complex and interesting.<br /><br />This film is bound to be enjoyed by anyone except for people who hate old horror films. You can really tell that Universal Pictures pulled out all the stops and made a bigger-budget film instead of the cheap quickies both Lugosi and Karloff unfortunately gravitated in later years. Good stuff.